(a) Colloid substances which accumulated in gut contents on absence or modification of the intestinal flora and which are responsible for impaired water absorption from the lower bowel, will be studied in germfree and antibiotic treated conventional animals. Of prime interest is the degradation of this "colloid bulk" which will be carried out in vitro and in vivo with enzyme preparations and/or selected bacterial cultures. (b) The effects of bioactive absorbable agents from the germfree and antibiotic treated gut will be studied in terms of epinephrine inhibitory substances. It will be attempted to clarify the nature, optimum conditions for activity and physiologic degradation of these substances.